Boat fender structures



July 15, 1969 D. L. DEAN 3,455,269

BOAT FENDER STRUCTURES Filed April 26, 1968 I NVENTOR. 51/ A. flm/v Arm?5/;

United States Patent US. Cl. 114219 17 Claims ABSTRACT OF THE DISCLOSUREA boat fender structure having several different bagged configurationsof buoyant material one inside of the other. The inside configurationcomprises relatively rigid, disc-shaped sections stacked one next to theother. The outer configurations comprise sheets of relatively resilient,buoyant material which are wrapped in the form of a spiral.

Cross-references to related applications This is a continuation-in-partof a copending application, Ser. No. 596,892, filed Nov. 25, 1966, nowabandoned.

Background of the invention This invention relates to boat fenders, andmore particularly, to new structures in buoyant, watertight boatfenders.

For many years cocoa and rope mats, pieces of cork, and solid nonporousrubber have served as boat fenders. These structures have proved usefulto reduce or eliminate damage upon collision of two boats or a boat witha dock by absorbing the impact in part and distributing it over a largerarea, but they sufier from nu merous shortcomings. For the most part,these fenders absorb water, are nonbuoyant and subject to fast wear, andlack the ruggedness and resilience to withstand for extended periods oftime the tremendous impacts that are encountered in normal use.

Recently a boat fender structure has been developed that overcomes theseshortcomings to a large extent. This structure comprises a hollow,rubber core around which sheets of buoyant resilient material are woundin the form of a spiral and cemented together. The resulting cylindricalbody is bagged, so to speak, in a snug-fitting, watertight cover.Fixtures mounted at either end of the structure are connected by a steelcable running through the hollow interior of the core. In use thesefenders are draped over the hull of the boat by lines secured to thefixtures. This fender structure has found wide acceptance because it iswatertight, buoyant, rugged, and resilient. In addition, it isfire-resistant and easy to clean and repair.

This improved boat fender, however, is not particularly well suited forall applications. For example, a fender used on a tugboat that ispushing another boat transmits a large, relatively constant forcebetween the tugboat and the other boat for sustained periods of time.This application calls for a more rigid'fender than applicationsinvolving short, intermittent impacts between boats. In otherapplications, boat fenders are required having large diameters. Byincreasing the diameter of a boat fender beyond a certain point, itsstrength with respect to axial forces is impaired. Large axial forcesgive rise to shear between the adjoining spiral surfaces of the buoyantmaterial wrapped as a spiral inside of the fender. As a result, theoutside layers tend to unravel in a direction parallel'to the axis andthe fender becomes permanently deformed or even completely destroyed.

Summary of the invention According to the invention, fender structuressuitable for the above-mentioned, as Well as other, applications areprovided. In one bagged structure, the buoyant material that surroundsthe core is formed from rigid discshaped sections stacked one next tothe other. This arrangement is capable of withstanding and transmittinglarge axial forces without deforming, due to the fact that the longdimension of each section of buoyant material is parallel to the appliedforce, much like the case of a structural beam. In addition, the stackedarrangement of sections obviates the need to bend sheets of the buoyantmaterial. Thus a buoyant material having high rigidity at normaltemperatures can be selected without having to heat the material inorder to bend it into a spiral unit.

In another structure, a bagged unit of buoyant material is utilized as acore around which sheets of buoyant material are wrapped in the form ofa spiral unit and bagged in a watertight cover. More bagged spiral unitsof buoyant material can be added to the structure as desired. Thus, thisfender structure comprises a plurality of bagged units of buoyantmaterial one inside of the other, which permits construction of fendershaving a large cylindrical diameter without impairing the strength withrespect to axial forces. The radial thickness of each spiral unit ofbuoyant material is maintained small enough so that the material doesnot tend to unravel upon exposure to the anticipated axial forces. Thestructure is built up to the desired diameter by simply adding morebagged units of buoyant material around the outside of the-alreadyexisting structure.

In still another structure, several separately bagged units of buoyantmaterial are provided that have different stressstrain characteristics.The buoyant material in the bagged units could be arranged in diiferentconfigurations and/or have different degrees of resiliency. As a result,a wide range of control can be exercised over the stress-straincharacteristics of the fender. In one embodmient, the innermost baggedunit is formed from a stacked configuration of rigid disc-shapedsections, as described above, while one or more outer units are formedfrom a spiral configuration of more resilient material. This embodimentprovides large strain at small values of stress and less strain atincreased values of stress. As a result, upon impact the fender providesa more gradual transfer of forces between colliding surfaces.

Brief description of the drawing The features of specific embodiments ofthe invention are illustrated in the drawing, in which:

FIG. 1 is a side view partially in section of a fender structure havingdisc-shaped sections of buoyant material stacked one next to the other;

FIG. 2 is a side view partially in section of a fender structureemploying the structure of FIG. 1 as a core around which sheets ofbuoyant material are wrapped; and

FIG. 3 is an end view in section of the structure of FIG. 2.

Description of specific embodiments In FIG. 1 a fender structure isshown having a hollow core 1 with a passage 14 through it. Core 1 couldbe made, for example, of hard rubber. Disc-shaped sections of rigid,buoyant material comprising a unit 2 are stacked next to each otheraround core 1. The contiguous surfaces of the sections are cementedtogether. The buoyant material used to make the sections of unit 2 couldbe, for example, a polyvinylchloride foam such as Type AF Ensolitemarketed by the United States Rubber Company. Core 1 and unit 2 arebagged in a snug-fitting, watertight, double cover 3 composed of severalpieces.

Cover 3 is watertight so that oil and other foreign substances do notpenetrate through it to the interior of the fender. Thus, foreignsubstances remain on the surface of cover 3 and can be easily washedoff. It is not essential, however, that cover 3 be watertight becausethe foam comprising the buoyant material has closed cells and thereforeabsorbs very little water. Rectangular pieces 4 and 5 are wrapped one ontop of the other around the cylindrical surface formed by the sectionsof unit 2. Circular pieces 6a, 6b, 7a, and 7!) cover the end surfaces ofthe cylinder formed by sections 2. Pieces 6a, 6b abut with the ends ofpiece 4. Pieces 7a, 7b overlap the ends of piece 5. Strips 8a, 8b ofrubberized tape seal the joint between pieces 7a, 7b, and piece 5,thereby sealing the structure. Cover 3 could be crossed, nylon tire cordcoated with neoprene. Pieces 4 and 5 are oriented such that the cordsrun along the surface of the fender 0n the bias as represented by lines11 and 12. Fixtures 13a, 1312 are mounted on the ends of the fender. Oneend of fixtures 13a, 13b fits firmly into passage 14 of core 1, whilethe other end protrudes from the end surface of the fender. Holes 15a,15b in fixtures 13a, 13b are employed to secure a line to the fender.Mounting plates 16a, 16!), which are integral parts of fixtures 13a,13b, are sandwiched between pieces 6a, 6b and core 1. Cover plates 17a,17b fit around the protruding part of fixtures 13a, 13b and are boltedto plates 16a, 16b. Tensile strength along the axis of the structure isprovided by a steel cable 18 that connects fixtures 13a, 13b throughpassage 14. In use on a tugboat or in any other application requiring arigid fender, unit 2 exhibits relatively little deformation uponapplication of radial forces to the fender. Furthermore, since thesections of unit 2 need not be bent, very rigid materials can beemployed without having to elevate the temperature during construction.

Reference is now made to FIGS. 2 and 3, in which another fenderstructure is shown. The fender structure of FIG. 1, designated as 22 inFIGS. 2 and 3, serves as a core in this structure. Sheets of buoyantmaterial are wrapped around the perimeter of core 22 in the form of aspiral unit 21 that is bagged in a single cover 20. More strips ofbuoyant material are wrapped around cover 20 to form a spiral unit 23.The entire structure is bagged in a sealed, watertight cover 25, similarin construction to cover 3 in FIG. 1. Cover plates 30a, 30b, analogousto plates 17a, 17b in FIG. 1, fit over cover and around the protrudingpart of fixtures 29a, 29b. The sheets of units 21 and 23 are cemented toeach other. As shown at points 24 and 28 in FIG. 3, the ends of thesheets cemented to the surface of core 22 and cover 20 are beveled toprovide a smooth transition therebetween. The material of units 21 and23 is preferably more resilient than the material of unit 2. It could,by way of example, be a polyvinylchloride foam material such as Type ALEnsolite marketed by the United States Rubber Company. Although thestructure illustrated in FIGS. 2 and 3 involves three bagged units ofbuoyant material located one within the other, the structure could beexpanded to include any number of bagged units. The units could compriseany configuration or combination of configurations of buoyant material.By separately bagging portions of the buoyant material, it is possibleto construct large diameter fenders having good strength against axialforces, because each cover lends added support to the buoyant materialcontained within it. Only the outermost cover need actually bewatertight to prevent foreign substances from entering the interior ofthe fender.

In the fender structure shown in FIGS. 2 and 3, the cover that bags core22 is preferably formed in a slightly different manner than cover 3 inthe fender structure of FIG. 1 so as to lend additional axial strength.Specifically, this cover is preferably made so the nylon tire cord runsalong the length of the fender, i.e. parallel to the axis of hollowcore 1. As a result, the tire cord strengthens the fender structure soit withstands axial forces better. The

neoprene-coated nylon tire cord is commercially available in sheets. Thecords in each sheet are all parallel. The sheets are cut parallel to thecords to form strips that are used to form the cover. Each strip extendsfrom one end of the unit of buoyant material it covers along the lengthof the unit, i.e. parallel to the axis of hollow core 1, and to theother end of the unit. The strips are cemented to the outer surface ofthe unit of buoyant material in overlapping relationship so thattogether they completely cover the buoyant material. Preferably, atleast some of the ends of the strips are anchored to fixtures 29a, 2%.This could be done by cutting a hole in the ends of the strips to beanchored and placing the ends of these strips around fixtures 29a, 29bso the ends of these strips are clamped between the mounting plates andthe cover plates, as depicted in FIG. 2. In addition, cover 25 ispreferably constructed from three layers of neoprenecoated tire cords.The outer layer has cords running along the surface of the fender on thebias in the direction of lines 11 in FIG. 1. The middle layer isconstructed like the previously described cover for core 22. In otherwords, the cords run along the length of the fender in the middle layer.The inner layer has cords running along the surface of the fender on thebias in the direction of lines 12.

In addition to having a plurality of bagged units of buoyant material,the structure of FIGS. 2 and 3 involves a combination of configurationsof buoyant material, i.e. spiral units 21 and 23 and unit 2 of stacked,discshaped sections. The use of a more resilient material for units 21and 23 than for unit 2 and the arrangement of the material in differentconfigurations yield different stress-strain characteristics for units21 and 23 than for unit 2. By varying these factors, i.e. the resiliencyof the materials and their configurations, control may be exercised overthe resultant stress-strain characteristics of the fender structure.Thus, the particular fender structure of FIGS. 2 and 3 exhibits largerate of change of strain upon initial application of stress and adecreased rate of change of strain for larger stress. As a result, thefender provides a more gradual transfer of forces between the collidingboats upon impact.

Preferably, the fender structures of the invention would have circularcross sections as shown in FIG. 3. It is con ceivable, however, thatfender structures employing the principles of the invention could beconstructed with oval cross sections. Thus, the term disc-shapedsections" is to be understood as including not only circular sectionsbut oval sections as well.

As a final step in the construction of the described fenders, it ispreferable to heat them under pressure so that the various parts fusetogether to some extent. The pressure could be provided by encapsulatingthe fenders in steel drums during heating. The drums confine the fendersto their original size as the buoyant material expands in the course ofthe application of heat, thereby generating pressure.

What is claimed is:

1. A boat fender comprising:

a plurality of rigid, buoyant, disc-shaped sections stacked one next tothe other as a first unit;

a first cover fitting snugly around the first unit;

a second unit of buoyant material surrounding the first cover; and

a second cover fitting snugly around the second unit of buoyantmaterial.

2. The boat fender of claim 1, in which the second unit comprises sheetsof buoyant material wrapped around the first cover in a spiralconfiguration.

3. The boat fender of claim 2, in which the buoyant material of thesecond unit is more resilient than the buoyant material of the firstunit.

4. The boat fender of claim 1, in which the buoyant material of thesecond unit is more resilient than the buoyant material of the firstunit.

5. The boat fender of claim 1, in which the second cover is watertight.

6. A boat fender comprising:

a first unit of buoyant material;

a first cover fitting snugly around the first unit of buoyant material;

a second unit of buoyant material surrounding the first cover;

a second cover fitting snugly around the second unit of buoyantmaterial;

a third unit of buoyant material surrounding the second cover; and

a third cover fitting snugly around the third unit of buoyant material.

7. The boat fender of claim 6, in which the third cover is watertight.

8. The boat fender of claim 6, in which at least two of the units ofbuoyant material have difierent stressstrain characteristics.

9. A boat fender comprising:

a hollow core having a passage through it;

a first unit of solid buoyant material disposed around the core;

a second unit of solid buoyant material surrounding the first unit, thesecond unit of buoyant material having different stress-straincharacteristics than the first unit of buoyant material;

a cover fitting snugly around the second unit of buoyant material;

a pair of fixtures protruding outwardly from the cover at the ends ofthe passage of the core; and

an elongated member connecting the fixtures through the passage of thecore to provide tensile strength.

10. The boat fender of claim 9, in which the buoyant material of oneunit is more resilient than the buoyant material of the other unit.

11. The boat fender of claim 9, in which the buoyant material of thesecond unit is more resilient than the buoyant material of the firstunit.

12. The boat fender of claim 9, in which the buoyant material of thefirst unit has a different configuration from the buoyant material ofthe second unit.

13. The boat tender of claim 12, in which the first unit is configuredof a plurality of rigid disc-shaped sections stacked one next to theother around the core.

14. The boat fender of claim 13, in which the second unit comprisessheets of resilient material wrapped around the first unit in a spiralconfiguration.

15. The boat tender of claim 12, in which the second unit comprisessheets of resilient material wrapped around the first unit in a spiralconfiguration.

16. The boat fender of claim 3, in which the disc shaped sections of thefirst unit are disposed around a hollow core having a passage throughit, a pair of fixtures that protrude outwardly from the second cover aremounted at the ends of the passage of the core, and an elongated memberproviding tensile strength connects the fixtures through the passage ofthe core.

17. The boat fender of claim '6, in which the first unit of buoyantmaterial is disposed around a hollow core having a passage through it, apair of fixtures that protrude outwardly from the third cover aremounted at the ends of the passage of the core, and an elongated memberproviding tensile strength connects the fixtures through the passage ofthe core.

References Cited UNITED STATES PATENTS 1,815,413 7/1931 Lockwood 1142192,885,989 5/1959 Williamson 114-219 3,113,546 12/1963 Mountcastle114-219 MILTON =BUCHLER, Primary Examiner J. E. PITTENGER, AssistantExaminer US. Cl. X.R.

